Sickles typically including cutter bars supporting a row of knives, have been used to cut plants, including, but not limited to, hay, grasses, small grains and the like, for many years. The knives are composed of a plurality of knife or sickle sections which are mounted in side by side relation forming an elongate metal knife assembly. The elongate knife assembly is normally supported so as to slide longitudinally through slots in, or over, forwardly projecting, spaced apart guards. The knife assembly moves back and forth in a reciprocating movement to move the knives relative to the guards so that the leading knife edges of the knives cross over the guards or through the slots in the guards. This produces a shearing or cutting action which severs plant stems and stalks or other material which flows into and is captured in the spaces between the knives and the guards.
In operation, as the crop cutting machine moves forwardly over a field, it is desirable for the plant stems and stalks to flow smoothly and uninterruptedly into the spaces between the guards, so as to be cleanly severed by the knives. It is also desired for the cut plant material to flow smoothly and largely uninterruptedly over the sickle, not bunch up thereon, and flow or fall onto a floor or pan of the header, particularly when the cutting machine is a harvester. Often, harvesters also include a rotary reel disposed over the sickle to facilitate the induction of the plants into the sickle, clear cut plant material from the sickle, and help move the cut crops onto the header floor. On the header, the cut crop material is typically conveyed sidewardly toward the center of the header, by an auger or belt, for induction into a feeder of the machine or other apparatus.
A problem that can occur, however, when cutting crops in the above manner, is that sometimes as a result of the cutting action, crops will not be inducted into the header, but instead will be lost. For instance, as a result of a dull or worn sickle, the crop stalks or stems may be jerked, bent, and/or torn instead of cleanly cut, which can shake grain loose from the crop before it enters the header, such that some of the loose grain can fall to the ground in front of the header. The bats or tines of reel can also strike the crops and shatter pods, etc., to loosen or thresh the grain so as to be lost, particularly under dry conditions. Still further, the augers for conveying the cut crops toward the center of the header can include fingers that operate to pull the cut crops into the auger, which can unintentionally thresh some of the grain from the crop. As a result, a significant amount of loose grain can be present in the forward region of a header, on and above the sickle and guards, which is at risk of loss if not conveyed or inducted onto the header.
Numerous devices and systems have been developed over many years, in attempts to blow loose grain toward the header. Reference in this regard, the system utilizing pressurized air directed through nozzles or jets on or in connection with the sickle guards disclosed in McDonnell U.S. Pat. No. 6,085,510, issued Jul. 11, 2000. However, an observed shortcoming of the embodiment of the system of the McDonnell patent illustrated in FIGS. 1-3 of that patent, is that the air nozzles or outlets are located in the slots of the guards in which the sickle knives move. In a second embodiment shown in FIG. 4 and subsequent Figures of the McDonnell patent, nozzles project sidewardly from the guards into the spaces between the adjacent guards, so as to be located in the crop flow paths along and between the guards. Reference also, Phillips U.S. Pat. No. 2,718,744, issued Sep. 27, 1955; and Klinger U.S. Pat. No. 2,737,006, issued Feb. 26, 1954. The Phillips and Klinger patents also utilize pressurized air nozzles, but located on structures on the guards or extending forwardly therefrom (Phillips massively so), and which also extend sidewardly into the crop flow path (more so in Klinger) so as to possibly interfere with crop flow to the cutting region between the sickle knife and side of the guard. Any outward projection of a nozzle into the crop flow path can result in contact with crop plants forwardly of the front edge of the header pan that can jar the plants, to cause them to drop grain, which can fall between the guards so as to be lost. The air flow ducts of Phillips and Klinger are also significantly larger than the guards and extend beneath the guards, so as to limit the positioning options of the guards and the header relative to the ground, particularly the closeness to the ground and the ability to orient the guards toward the ground. The Phillips and Klinger air flow ducts are also exposed to damage from contact with the ground.
Thus, what is sought is an air discharge system for guards of a sickle of a header of an agricultural plant cutting machine, that is effective for discharging flows of air rearwardly, for directing loose grain and other crop elements toward the header, yet which is unobtrusive and overcomes one or more of the problems, disadvantages, and shortcomings referenced above.